The present invention generally relates to a cannula-penetrable, self-sealing, gas proof closure for sealing an open end of an air evacuated blood collection tube, and more particularly, concerns a low penetration force closure for blood collection tubes with an indicator for visibly determining whether a vacuum condition is present inside the blood collection tube.
Self-sealing, gas proof elastomeric closures of various configurations are used extensively for sealing an open end of an air evacuated blood collection tube. These type closures not only provide an effective seal for maintaining a vacuum inside the collection tube, but also are penetrable by a cannula so that fluids may be deposited or withdrawn from the container without compromising the sterility of the container. While these types of closures have been utilized for a long time, improvements in their use and features are continually being sought. For example, U.S. Pat. No. 4,111,326 explains many deficiencies of prior closures, while offering improvements over these prior art closures, such as the use of less material for construction, reduction in manufacturing expense, easier assembly and a much lower force to penetrate with a needle, amongst other areas of improvement.
In addition to the many deficiencies of prior art closures as pointed out in U.S. Pat. No. 4,111,326, other problems arise in the use of air evacuated blood collection tubes. Specifically speaking, some blood collection tubes are inoperable due to the fact that something has caused the vacuum conditions inside the blood collection container to dissipate. These collection tubes, sometimes referred to in the art as "dead tubes," are not only non-functional, but also are oftentimes undetectable when "dead." In many instances, it is not until the operator of the collection tube is attempting to collect blood that it is realized that there is no vacuum inside the container.
Instead of relying upon effective quality control procedures to provide a favorable statistical expectation that the blood collection tube will work, a readily discernible, positive indication that each and every blood collection tube has the proper vacuum conditions is still being sought. While U.S. Pat. No. 4,111,326 indeed recognizes such a vacuum determination problem, and seeks to address and correct the same, it is not entirely successful in providing a superior indicator to the operator of the vacuum conditions inside the tube. For example, the means to determine the degree of vacuum loss such as measurement of bore depth or mechanical and optical means of measuring the curvature of the diaphragm at the bottom of the closure, may be time consuming and involve use of extra equipment. An improved way of determining whether or not the blood collection tube has the proper vacuum conditions is therefore still being sought, especially if such an improvement could be combined with the advantageous features of the closure described in U.S. Pat. No. 4,111,326. With such an improvement in mind, the present invention is hereby directed.